Absorbent sheets having high absorbency and high caliper, and methods of making soft, absorbent sheets

ABSTRACT

An absorbent cellulosic sheet made by a method that includes forming an aqueous cellulosic web on a structuring fabric in a papermaking machine, non-compactively dewatering the cellulosic web on the structuring fabric, and drying the cellulosic web to form the absorbent cellulosic sheet. A portion of the structuring fabric on which the cellulosic web is formed has an adjusted planar volumetric index of at least about 27.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 15/191,785, filed Jun. 24, 2016, now U.S. Pat. No. 9,611,591,which is a divisional of U.S. patent application Ser. No. 14/541,380,filed Nov. 14, 2014, now U.S. Pat. No. 9,404,224, which is anon-provisional application based upon U.S. Provisional PatentApplication No. 61/904,177, filed on Nov. 14, 2013, which areincorporated herein by reference in their entirety.

BACKGROUND

Field of the Invention

Our invention relates to paper products such as absorbent hand towels.Our invention also relates to processes of manufacturing paper productssuch as absorbent hand towels.

Related Art

It is desirable for many types of paper products to have diverseproperties. For example, absorbent paper products must be able to mop uplarge amounts of liquid before becoming saturated. As another example,customers greatly prefer that absorbent paper products feel soft to thetouch. Absorbency and softness, however, are contradictory propertieswhen it comes to manufacturing paper products. Most techniques forincreasing the absorbency of paper products will also have the effect ofdecreasing the perceived softness of the products. Conversely, mosttechniques for increasing the softness of paper products will have theeffect of decreasing the absorbency of the products. For example,calendering basesheets that make up the paper products can increase thesoftness of the products. Calendering, however, also has the effect ofreducing the caliper of the basesheets. And, as absorbency of paperproducts is generally proportional to the caliper of the products,calendering the basesheets will also have the effect of reducing theabsorbency of the products. The use of wet and dry strength resins areexamples of other techniques that improve the properties of paperproducts. Such resins are added to the furnish used in a papermakingprocess, and the resins have the effect of improving the underlyingstrength of the resulting paper products, e.g., the cross machinedirection (CD) or machine direction (MD) wet tensile strength of theproducts. Wet and dry strength resins, however, also have theundesirable effect of reducing the perceived softness of the resultingproducts.

Another challenge in manufacturing paper products is that paper makingis a relatively low margin industry, and, thus, there is a constant needto find more economically efficient products and processing. In terms ofproducts, the basis weight or bulk of paper products are properties thatare often studied in an attempt to devise more economical products.There is a constant search for paper products that have a lower basisweight or higher bulk, but still have comparable properties in all otheraspects.

SUMMARY OF THE INVENTION

According to one aspect, our invention provides a method of making apaper product. The method includes forming an aqueous cellulosic web ona structuring fabric in a papermaking machine, non-compactivelydewatering the cellulosic web on the structuring fabric, and drying thecellulosic web to form the paper product. A portion of the structuringfabric on which the cellulosic web is formed has an adjusted planarvolumetric index of at least about 27.

According to a further aspect, our invention provides a method of makinga paper product. The method includes forming an aqueous cellulosic webon a structuring fabric in a papermaking machine, non-compactivelydewatering the cellulosic web on the structuring fabric, and drying thecellulosic web to form the paper product. A portion of the structuringfabric on which the cellulosic web is formed has an adjusted planarvolumetric index of at least about 27 during (i) an initial period inwhich the cellulosic web is formed on the structuring fabric on thepapermaking machine and (ii) after the structuring fabric is run forabout 950,000 cycles of operation of the papermaking machine.

According to yet another aspect, our invention provides a papermakingmachine for making a paper product using a through air drying process.The papermaking machine includes a headbox for supplying a furnish. Thepapermaking machine also includes a structuring fabric having a surfacewith a contact area, the structuring fabric being configured (i) toreceive the furnish from the headbox on the surface to thereby form acellulosic web from the furnish and (ii) to non-compactively dewater thecellulosic web. The portion of the structuring fabric on which thecellulosic web is formed has an adjusted planar volumetric index of atleast about 27.

According to a still further aspect, our invention provides an absorbentcellulosic sheet. The sheet is made by a method that includes forming anaqueous cellulosic web on a structuring fabric in a papermaking machine,non-compactively dewatering the cellulosic web on the structuringfabric, and drying the cellulosic web to form the absorbent cellulosicsheet. A portion of the structuring fabric on which the cellulosic webis formed has an adjusted planar volumetric index of at least about 27.

According to yet another aspect, our invention provides process ofdetermining features of a fabric. The process includes forming arepresentation of a portion of a surface of the fabric, therepresentation showing locations and sizes of knuckles and pockets inthe surface of the fabric, and the representation being one of a printof the fabric surface and a photograph of the surface of the fabric. Theprocess further includes generating an image of the portion of thesurface of the fabric based on the representation, displaying at least aportion of the image on a screen associated with a computer having aprocessor, determining the sizes and locations of the knuckles in thedisplay of the representation, and determining the sizes and locationsof the pockets in the display of the representation. The process stillfurther includes drawing a unit cell for the portion of the surface ofthe fabric in the displayed image, wherein the unit cell is defined byguidelines that (i) pass through the centers of the knuckles and (ii)form shapes that surround areas of the image that correspond to wherethe pockets are formed between the knuckles, and calculating a planarvolumetric index of the fabric based on properties of the unit cellformed by the guidelines. The outline and guidelines are drawn using animage analysis program stored in a non-transitory computer-readablemedium.

According to a further aspect, our invention provides a process ofdetermining features of a fabric. The process includes forming arepresentation of a portion of a surface of the fabric, therepresentation showing locations and sizes of knuckles and pockets inthe surface of the fabric, and the representation being one of a printof the fabric surface and a photograph of the surface of the fabric,generating an image of the portion of the surface of the fabric based onthe representation, displaying at least a portion of the image on ascreen associated with a computer having a processor, determining thesizes and locations of the knuckles in the display of therepresentation, and determining the sizes and locations of the pocketsin the display of the representation. The process further includesdrawing a unit cell for the portion of the surface of the fabric in thedisplayed image, wherein the unit cell is defined by guidelines that (i)pass through the centers of the knuckles and (ii) form shapes thatsurround areas of the image that correspond to where the pockets areformed between the knuckles, and calculating an adjusted planarvolumetric index of the fabric based on properties of the unit cellformed by the guidelines. The outline and guidelines are drawn using animage analysis program stored in a non-transitory computer-readablemedium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a papermaking machine configurationthat can be used in conjunction with our invention.

FIGS. 2A and 2B are photographs of the web contacting surfaces ofstructuring fabrics.

FIG. 3 is a top view of a structuring fabric for making productsaccording to our invention.

FIGS. 4A and 4B are views of a contact surface printing apparatus.

FIG. 5 is a detailed view of the pressing section of the contact surfaceprinting apparatus shown in FIGS. 4A and 4B.

FIGS. 6A through 6D are examples of prints of structuring fabrics.

FIGS. 7A through 7E show the steps of establishing a coordinate systemin a print of a structuring fabric.

FIGS. 8A through 8C show the application of our analytic techniqueherein as it is applied to a photograph of the knuckles of a structuringfabric.

FIGS. 9A and 9B show an alternative analytic technique applied to aphotograph and print of the knuckles of a structuring fabric.

FIG. 10 shows the application of an analytic technique to determine apocket surrounded by knuckles in the structuring fabric shown in FIG. 3.

FIG. 11 shows the application of an analytic technique to determine thedepth of the pocket shown in FIG. 10.

FIGS. 12A through 12D show planar volumetric indexes for a structuringfabric that can be used to make the products of the invention and planarvolumetric indexes for comparative structuring fabrics.

FIG. 13 is a plot showing the relation of caliper and SAT capacity fortrial products according to the invention and for comparative products.

FIG. 14 is a plot showing the relation of tensile ratio and caliper fortrial products according to the invention and for comparative products.

FIG. 15 is a plot showing the relation of tensile ratio and SAT capacityfor trial products according to the invention and for comparativeproducts.

FIG. 16 is a plot showing the relation of stretch ratio and SAT capacityfor trial products according to the invention and for comparativeproducts.

FIG. 17 is a plot showing the relation of stretch ratio and caliper fortrial products according to the invention and for comparative products.

DETAILED DESCRIPTION OF THE INVENTION

Our invention relates to absorbent paper products and methods of makingabsorbent paper products. The absorbent paper products according to ourinvention have outstanding combinations of properties that are superiorto other paper products that are known in the art. In some specificembodiments, the paper products according to our invention havecombinations of properties particularly well suited for absorbent handtowels.

The term “paper product,” as used herein, encompasses any productincorporating papermaking fibers having cellulose as a majorconstituent. This would include, for example, products marketed as papertowels, toilet paper, facial tissues, etc. Papermaking fibers includevirgin pulps or recycle (secondary) cellulosic fibers, or fiber mixescomprising cellulosic fibers. Wood fibers include, for example, thoseobtained from deciduous and coniferous trees, including softwood fibers,such as northern and southern softwood kraft fibers, and hardwoodfibers, such as eucalyptus, maple, birch, aspen, or the like. Examplesof fibers suitable for making the products of our invention includenon-wood fibers, such as cotton fibers or cotton derivatives, abaca,kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse,milkweed floss fibers, and pineapple leaf fibers.

“Furnishes” and like terminology refers to aqueous compositionsincluding papermaking fibers, and, optionally, wet strength resins,debonders, and the like, for making paper products. A variety offurnishes can be used in embodiments of our invention. In someembodiments, furnishes are used according to the specificationsdescribed in U.S. Pat. No. 8,080,130 (the disclosure of which isincorporated by reference in its entirety). The furnishes in this patentinclude, among other things, cellulosic long fibers having a coarsenessof at least about 15.5 mg/100 mm. Examples of furnishes are alsospecified in the product examples discussed below.

As used herein, the initial fiber and liquid mixture that is dried to afinished product in a papermaking process will be referred to as a “web”and/or a “nascent web.” The dried, single-ply product from a papermakingprocess will be referred to as a “basesheet.” Further, the product of apapermaking process may be referred to as an “absorbent sheet.” In thisregard, an absorbent sheet may be the same as a single basesheet.Alternatively, an absorbent sheet may include a plurality of basesheets,as in a multi-ply structure. Further, an absorbent sheet may haveundergone additional processing after being dried in the initialbasesheet forming process in order to form a final paper product from aconverted basesheet. An “absorbent sheet” includes commercial productsmarketed as, for example, hand towels.

The term “directly attached” when used in reference to a first ply and asecond ply of products means that the two plys are attached to eachother without any intermediate ply. The first ply thereby forms a firstsurface of the sheet, and the second ply thereby forms a second surfaceof the sheet. In this regard, a “ply” refers to a sheet structure madeof papermaking fibers having cellulose as a major constituent, and doesnot encompass, for example, a glue used to directly attach two plystogether. Those skilled in the art will recognize the numeroustechniques for directly attaching two or more plys together into a paperproduct.

When describing our invention herein, the terms “machine direction” (MD)and “cross machine direction” (CD) will be used in accordance with theirwell-understood meaning in the art. That is, the MD of a fabric or otherstructure refers to the direction that the structure moves on apapermaking machine in a papermaking process, while CD refers to adirection crossing the MD of the structure. Similarly, when referencingpaper products, the MD of the paper product refers to the direction onthe product that the product moved on the papermaking machine in thepapermaking process, and the CD of the product refers to the directioncrossing the MD of the product.

FIG. 1 shows an example of a papermaking machine 10 that can be used tomake paper products according to our invention. The papermaking machine10 is configured for a through air drying (TAD) papermaking process inwhich a structuring fabric 48 is used to form the three-dimensionalstructure of the paper product. To begin the process, furnish suppliedthrough a head box 20 is directed in a jet into a nip formed between aforming fabric 24 and a transfer fabric 28. The forming fabric 24 andthe transfer fabric 28 pass between a forming roll 32 and a breast roll36, and then diverge after passing between the forming roll 32 and thebreast roll 36. At this point, the furnish has been formed into anascent web on the transfer fabric 28. The transfer fabric 28 thenpasses through dewatering zone 40 in which suction boxes 44 removemoisture from the web and the transfer fabric 28, thereby increasing theconsistency of the web, for example, from about 10% to about 25% priorto transfer of the web to the structuring fabric 48. In some instances,it will be advantageous to apply a vacuum through vacuum assist boxes 52in the transfer zone 56, particularly, when a considerable amount offabric crepe is imparted to the web in the transfer zone 56 by a rushtransfer wherein the transfer fabric 28 is moving faster than thestructuring fabric 48.

Because the web still has a high moisture content when it is transferredto the structuring fabric 48, the web is deformable such that portionsof the web can be drawn into pockets formed between the yarns that makeup the structuring fabric 48. (The pockets in structuring fabrics willbe described in detail below.) As the structuring fabric 48 passesaround through dryers 60 and 64, the consistency of the web isincreased, for example, from about 60% to about 90%. The web is therebymore or less permanently imparted with a shape by the structuring fabric48 that includes domes that are formed where the web is drawn into thepockets of the structuring fabric 48. Thus, the structuring fabric 48provides a three-dimensional shape to the web that results in a paperproduct having dome structures.

To complete the paper forming process, the web is transferred from thestructuring fabric 48 to a Yankee dryer 68. The transfer can beaccomplished without a major degradation of the properties of the web,by contacting the web with adhesive sprayed onto the Yankee dryer 68.After the web reaches a consistency of about 96% or greater, a furthercreping is used to dislodge the web from the Yankee dryer 68, and then,the web is taken up by a reel 70. The speed of the reel 70 can becontrolled relative to the speed of the Yankee dryer 68 to adjust thefurther crepe that is applied to the web as it is removed from theYankee dryer 68.

The basesheets on reel 70 may then be subjected to further processing,as is known in the art, in order to convert the basesheets into specificproducts. For example, the basesheets may be embossed, and twobasesheets can be combined into multi-ply products. The specifics ofsuch a converting are discussed below in conjunction with the specifictrial examples of products according to our invention.

While FIG. 1 demonstrates one type of process in which a structuringfabric is used to impart a three-dimensional shape to a paper product,there are numerous alternative papermaking processes in which astructuring fabric is used. For example, a structuring fabric may beused in a papermaking process that does not utilize through air drying(TAD). An example of such a “non-TAD” process is disclosed in U.S. Pat.No. 7,494,563, the disclosure of which is incorporated by reference inits entirety. As will be appreciated by those skilled in the art, theinvention disclosed herein is not necessarily limited to any particularpapermaking process.

FIGS. 2A and 2B are magnified photographs of structuring fabrics of thetype that can be used as the structuring fabric 48 in the papermakingmachine 10 shown in FIG. 1. These figures show the surfaces of thefabrics that contact the web in papermaking processes. FIGS. 2A and 2Bare conventional structuring fabrics that are well known in the art. Thewarp and weft threads that make up the body of the structuring fabricscan be seen in FIGS. 2A and 2B.

FIG. 3 is a detailed drawing of a portion of the web contacting side ofthe structuring fabric having a configuration for forming productsaccording to our invention. The fabric includes warp yarns 202 that runin the machine direction (MD) when the fabric is used in a papermakingprocess, and weft yarns 204 that run in the cross machine direction (CD)when the fabric is used in a papermaking process. The warp and weftyarns 202 and 204 are woven together so as to form the body of thefabric. The actual contact surface of the fabric is formed by theknuckles 206, which are formed on the warp yarns 202, but not formed onthe weft yarns 204. That is, the knuckles 206 are in a plane that makesup the contact surface of the fabric. Pockets 210 (shown as the outlinedareas in FIG. 3) are defined in the areas between the knuckles 206.During a papermaking operation, portions of the web can be drawn intothe pockets 210, and it is the portions of the web that are drawn intothe pockets 210 that result in dome structures that are present in theresulting paper product, as described above.

As also described above, softness, absorbency, and caliper are threeimportant properties for many types of absorbent paper products. We havefound that all three of these properties may be affected by theconfiguration of the structuring fabric used in the process to form theproducts. In particular, we have found that the softness, absorbency,and caliper of the absorbent paper products may be influenced by theamount of contact area of the structuring fabric, that is, the areaformed by the knuckle surfaces of the structuring fabric that the webcontacts in the papermaking process. The softness, absorbency, andcaliper of the resulting paper products may also be influenced by thesize of the pockets between the knuckles in the structuring fabric. Withthese findings in mind, we have found that a highly useful manner ofcharacterizing a structuring fabric, such as the fabrics shown in FIGS.2A, 2B, and 3, is in terms of a “planar volumetric index.” The planarvolumetric index includes two variables: the contact area ratio (CAR)and the effective pocket volume (EPV). The contact area ratio is definedas the ratio of the contact area formed by the knuckles to the open areain the web contacting side of the structuring fabric. The effectivepocket volume is defined as an average volume of the pockets in thestructuring fabric into which cellulosic fibers of the web may migrateduring the papermaking operation. The planar volumetric index is definedas the contact area ratio (CAR) multiplied by the effective pocketvolume (EPV) multiplied by one hundred, i.e., CAR×EPV×100. As will bediscussed in further detail below, the structuring fabrics used to formthe inventive products and used to practice the inventive methodsdisclosed herein have a significantly higher planar volumetric indexthan other fabrics known in the art.

In order to calculate the planar volumetric index for a structuringfabric, the contact area ratio and the effective pocket volume must bemeasured. Those skilled in the art will recognize that differenttechniques may be used for measuring the parameters that make up theplanar volumetric index of a structuring fabric. Examples of specifictechniques that we use for calculating the contact area ratio and theeffective pocket volume of structuring fabrics will now be described.

The contact area of a fabric may be measured by the technique describedbelow. Further details of the following technique, which is alsodescribed in U.S. Patent Application Publication No. 2014/0133734, nowU.S. Pat. No. 9,349,175, U.S. Patent Application Publication No.2014/0130996, now U.S. Pat. No. 9,062,416, and U.S. Patent ApplicationPublication No. 2014/0254885, now U.S. Pat. No. 9,382,663 (thedisclosures of which are incorporated by reference in their entirety),will be described below.

The contact area ratio measurement begins with forming a representationof the knuckles and pockets of the web contacting side of thestructuring fabric. One type of representation is a print of thestructuring fabric. In this regard, an apparatus and a technique forforming a print of the contact surface formed by the knuckles of afabric is shown in FIGS. 4A and 4B. FIG. 4A is a side view of a contactsurface printing apparatus 300, and FIG. 4B is a front view of thecontact surface printing apparatus 300. This printing apparatus 300includes a C-shaped frame 302 with first and second arms 303 and 305. Afirst plate 304 is movably supported by the first arm 303, and astationary second plate 306 is supported by the second arm 305. A printof the knuckles of a fabric is formed between the first and secondplates 304 and 306, as will be described in detail below.

The first plate 304 is operatively connected to a hand-operatedhydraulic pump 308 for actuating movement of the first plate 304 towardsthe second plate 306. The pump 308 has a release valve for allowing thefirst plate 304 to be retracted from the second plate 306. The pump 308,however, can take many other forms so as to effect movement of the firstplate 304. The pump 308 may be connected to a transducer and transducerindicator 310 for measuring the pressure applied by the pump 308 to thefirst plate 304 as the first plate 304 is pressed against the secondplate 306. As a specific example, an ENERPAC® Hydraulic Hand Pump ModelCST-18381 by Auctuant Corp. of Milwaukee, Wis., can be used. As aspecific example of the pressure transducer, a Transducer TechniquesLoad Cell Model DSM-5K with a corresponding indicator, made byTransducer Techniques, Inc., of Temecula, Calif., can be used. Ofcourse, in other embodiments, the pump 308, the pressure transducer, andthe transducer indicator 310 may be combined into a single unit.

The frame 302 of the contact surface printing apparatus 300 includeswheels 311 adjacent to the front end of the frame 302, as well as amount 313 that may be used to hold the pump 308 and/or transducerindicator 310. One or more wheels 311 provided to the frame 302 make theframe 302 easier to move. An advantageous feature of the contact surfaceprinting apparatus 300, according to embodiments of the invention, isits portability. For example, with a configuration as shown in FIGS. 4Aand 4B, the printing apparatus 300 may be easily moved about sections ofa fabric that are mounted on a papermaking machine. As will certainlybecome appreciated by those skilled in the art, the ability to formprints of the contact surface of a fabric while the fabric is mounted toa papermaking machine, and, thus, to characterize the fabric accordingto the techniques described below, provides numerous benefits. As butone example, the wearing of a fabric on a papermaking machine can easilybe monitored by using the contact surface printing apparatus 300 to takeprints of the knuckles of the fabric after different periods ofoperation of the papermaking machine.

While the contact surface printing apparatus 300 shown in FIGS. 4A and4B includes a frame structure 302 that connects the first and secondplates 304 and 306, in other embodiments, a contact surface printingapparatus 300 need not include such a single frame structure 302.Instead, the first and second plates 304 and 306 may be non-connectedstructures that are individually aligned to form the print of a fabric.In still other embodiments, the plates 304 and 306 may take vastlydifferent forms from those depicted in FIGS. 4A and 4B. For example, oneof the plates 304 and 306 could be formed as an extended surface, whilethe other plate is formed as a circular structure that is rolled acrossthe extended surface. The term “plate,” as used herein, is a broad termthat encompasses any structure sufficient for contacting and/orsupporting the components for making the print of the fabric.Additionally, as is clear from the description above, the relativemotion of the first and second plates 304 and 306 in any embodimentcould be reversed, such that the second plate 306 is made movable, whilethe first plate 304 is held stationary.

FIG. 5 is a detailed view of Section A of the contact surface printingapparatus 300 shown in FIG. 4A, with the printing apparatus 300 beingset up to make a print of a section of a structuring fabric 312. Thestructuring fabric 312 is positioned between the plates 304 and 306, anda strip of pressure measurement film 314 is positioned against thestructuring fabric 312. Between the pressure measurement film 314 andthe first plate 304 is one or more sheets of paper 316. Between thestructuring fabric 31 and the second plate 306 is a strip of rubber 318.

Pressure measurement film is a material that is structured such that theapplication of force upon the film causes microcapsules in the film torupture, producing an instantaneous and permanent, high-resolution imagein the contacted area of the film. An example of such a pressuremeasurement film is sold as Prescale film by Fujifilm HoldingsCorporation of Tokyo, Japan. Another example of pressure measurementfilm is Pressurex-Micro® by Sensor Products, Inc., of Madison, N.J.Those skilled in the art will recognize that other types of pressuremeasurement films could be used in the printing techniques describedherein. In this regard, it should be noted that for the analysistechniques described below, the pressure measurement film need notprovide an indication of the actual pressure applied by the fabric tothe film. Instead, the pressure measurement film need only provide aprint image showing the contact surface formed by the knuckles of afabric.

The pressure applied to first plate 304 when forming a print of fabric312 on pressure measurement film 314 can be selected so as to simulatethe pressure that would be applied to a web against the fabric 312 in anactual papermaking process. That is, the pump 308 may be used togenerate a pressure (as measured by the transducer) on the first plate304 that simulates the pressure that would be applied to a web againstthe fabric 312 in a papermaking process. In the papermaking processdescribed above in conjunction with FIG. 1, the simulated pressure wouldbe the pressure that is applied to the web against the fabric 48 to theYankee dryer 68. In some papermaking processes, such as theaforementioned U.S. Pat. No. 7,494,563, the pressure applied to the webagainst the fabric 48 is generally in the range of six hundred psi.Accordingly, to simulate this papermaking process, six hundred psi ofpressure would be applied by the hydraulic pump 308 to the first plate304 when forming the image of the knuckles of fabric 312 in the pressuremeasurement film 314. For such an operation, it has been found thatmedium pressure 10-50 MPa Presclace film by FujiFilm can provide a goodimage of the knuckles of a structuring fabric.

Referring again to FIG. 5, the paper 316 acts as a cushion to improvethe print of the fabric 312 formed on the pressure measurement film 314.That is, the paper 316 provides compressibility and a smooth surface,such that the knuckles of the fabric 312 may “sink” into the pressuremeasurement film 314, which, in turn, forms a high resolution image ofthe knuckles in the pressure measurement film 314. To provide theseproperties, construction and kraft are examples of types of paper thatcan be used for the film 314.

The strip of rubber 318 creates a level contact surface for supportingthe fabric 312. In embodiments of the invention, the plates 304 and 306are made of a metallic material, such as steel. A steel plate mostlikely has imperfections that reduce the quality of the print of theknuckles of the fabric 312 formed in the pressure measurement paper 316.The paper 316 and the rubber 318 that are used between the plates 304and 306, and the pressure measurement film 314 and the fabric 312,however, provide a more level contact surface than do the surfaces ofthe metallic plates 304 and 306, thereby resulting in better imagesbeing formed in the pressure measurement film 314. Those skilled in theart will recognize that other alternative materials to the paper 316 andrubber 318 may be used as structures to provide the level surfacesbetween the plates 304 and 306 of the printing apparatus 300.

In other embodiments, a print is made of the knuckles of a fabric inmaterials other than pressure measurement film. Another example of amaterial that can be used to form prints of a fabric is wax paper. Aprint of the contact surface of a fabric may be made in a wax surface bypressing the contact surface of the fabric against the wax paper. Theprint in the wax paper can be made using the plates 304 and 306 in theprint apparatus 300 described above, or with other configurations of theplates. The wax paper print can then be analyzed in the same manner as apressure measurement film print, as will be described below.

FIGS. 6A through 6D show examples of prints of knuckles formed inpressure measurement film using the contact surface printing apparatus300. In these prints, the distinctive shapes and patterns of theknuckles of the fabrics can be seen. As discussed above, the knucklesform the contact surface for the fabric. Hence, high resolution printsof the knuckles in a pressure measurement film, such as those shown inFIGS. 6A through 6D, provide an excellent representation of the contactsurface of a fabric.

Next, a system for analyzing the prints of knuckles, such as those shownin FIGS. 6A through 6D, will be described. In the system, graphicalanalysis will be conducted on a conventional computer system. Such acomputer system will include well-known components, such as at least onecomputer processor (e.g., a central processing unit or a multipleprocessing unit) that is connected to a communication infrastructure(e.g., a communications bus, a cross-over bar device, or a network). Afurther component of the computer system is a display interface (orother output interface) that forwards video graphics, text, etc., fordisplay on a display screen. The computer system may still furtherinclude such common components as a keyboard, a mouse device, a mainmemory, a hard disk drive, a removable-storage drive, a networkinterface, etc.

As a first step in the analysis, a print of the contact area of theknuckles of a fabric is converted to a computer readable image using aphotoscanner. Any type of photoscanner may be used to generate thecomputer readable image; however, a photoscanner having at least 2400dots per inch (dpi) has been found to provide a good image for analysis.With the resolution of the scan of the image, an imaging analysisprogram can apply an exact scale to the image, and the exact scalingwill be used in the calculation of the surface characteristics of thestructuring fabric (as will be described below).

The scanned image may be stored in a non-transitory computer-readablemedium in order to facilitate the analysis described below. Anon-transitory computer readable medium, as used herein, comprises allcomputer-readable media except for a transitory, propagating signal.Examples of non-transitory computer readable media include, for example,a hard disk drive and/or a removable storage drive, representing a diskdrive, a magnetic tape drive, an optical disk drive, etc.

The scanned image, as well as characteristics of the contact surfacescanned image that are determined according to the techniques describedbelow, may be associated with a database. A “database,” as used herein,means a collection of data organized in such a way that a computerprogram may quickly select desired pieces of the data that constitutethe database. An example is an electronic filing system. In someimplementations, the term “database” may be used as shorthand for a“database management system.”

In order to perform quantitative analysis of the scanned print image, animage analysis program is used with the scanned images of the knucklesof a fabric. Such an image analysis program is developed, for example,with computational software that works with graphical images. Oneexample of such computational development software is MATHEMATICA® byWolfram Research, Inc., of Champaign, Ill. As will be described below,the image analysis program will be used to specifically identify theknuckles in the fabric print image of the structuring fabric, and, withknown scaling of the fabric print image, the image analysis program cancalculate the sizes of the knuckles and estimate sizes of the pockets.

When analyzing the scanned image, any size area that includes aplurality of knuckles and a pocket could be used for the analysisdescribed below. In specific embodiments, it has been found that a 1.25inch by 1.25 inch area of an image of a fabric allows for a goodestimation of properties, such as pocket sizes using the techniquesdescribed herein. In particular, it has been found that when an image isformed with a 2400 dpi resolution (discussed above), and using a 1.25inch by 1.25 inch area of image for the analysis, a goodcharacterization of the contact surface can be conducted. Of course,other resolutions and/or area may also provide good results.

FIGS. 7A through 7E depict the steps of identifying the knuckles in amagnified portion of the scanned image of a print using the imageanalysis program. Initially, as shown in FIG. 7A, a magnified portion ofan image 600 is viewed on the display screen of the computer systemrunning the analysis program. The image 600, which may be formed usingthe print technique described above, shows the knuckles 602. Along withusing the image 600 with the analysis program, the scaling of the image600 can be input into an analysis program. Such a scaling may be input,for example, as 2400 dpi, from which the analysis program can apply thescale SC to the image 600. The analysis program will then use the scaleto calculate the sizes and positions of the knuckles, as describedbelow.

FIGS. 7B and 7C show steps for identifying a specific knuckle 602A usingthe analysis program. The knuckle 602A is initially selected based onits location at a center region of the magnified image 600. In thisstep, a rough outline of the knuckle 602A is applied. The rectangularbox 604, which may be a stored shape in the analysis program, isinitially applied around the knuckle 602A in order to initiate theknuckle identification process. The initial rectangular box 604 shapemay then be more closely refined to match the shape of the knuckle 602A,as shown in FIG. 7C. In this case, the ends 606 and 608 are reshaped tobe more rounded, and, thus, they more closely correspond to the ends ofthe knuckle 602A. Although not shown, further refinements could be madeto the outline of the knuckle 602A until a sufficient match is made.Such refinements might be conducted by further magnifying the image 600.

As shown in FIG. 7D, after the knuckle 602A is identified by theoutline, guidelines 610 and 612 are drawn. The guidelines 610 and 612are each drawn so as to pass through the center of the knuckle 602A andextend in straight lines through the centers of the other knuckles.Notably, the guidelines 610 and 612 are also drawn to not cross theareas where pockets are formed in the fabric, which are known tocorrespond to the areas between groups of knuckles. By drawing theguidelines 610 and 612 straight between the centers of the knuckles, theguidelines 610 and 612 do not cross the area of the pockets that areformed between the knuckles.

After the guidelines 610 and 612 are drawn, as shown in FIG. 7E, furtherguidelines are drawn. These guidelines are drawn in a similar manner toguidelines 610 and 612, i.e., through the centers of the knuckles andnot passing through areas where pockets are formed. To aid in theprocess of drawing the guidelines, a lower magnification may be used.With the guidelines, a coordinate system is, in effect, established forthe positions of the knuckles. The analysis program, therefore, can nowidentify the size and shape of the knuckles based on the outline, andcan identify the locations of the knuckles as determined by the pointswhere the guidelines cross. The analysis program further has the scaleSC of the image 600 input. It follows that the analysis program canapply the scale to the outline knuckle 602A and the knuckle positioning,to calculate the actual sizes and spacing of the knuckles. Note, aswell, that the analysis program may calculate the frequency of theguidelines such as the number of times that the guidelines 612 crossguideline 610 per a unit length. The frequency of each set of guidelines610 and 612 will be used in calculations of properties of the fabric,and in other aspects of the invention, as will be described below.

It should be noted that, as shown in FIGS. 7D and 7E, the knuckles areall about the same size and all about the same shape, and the knucklesare regularly spaced along the guidelines. This is not surprising,inasmuch as most fabrics for papermaking machines are manufactured withhighly consistent yarn patterns, which results in very consistentknuckle sizes and positions. The consistency in size, shape, andplacement of the knuckles allows for accurate estimates of the size andshapes of all the knuckles on the contact surface of a fabric based on asingle selected knuckle, or on a limited number of identified knuckles,and a close estimate of the sizes and locations of the knuckles can beachieved without identifying each knuckle. Of course, to achieve evenfurther accuracy, more than one knuckle could be identified, and theoutlines and guidelines could be drawn at different portions of animage.

As shown in FIG. 7E, the guidelines 610 and 612 define a plurality ofunit cells. A particular unit cell 613 is shown between guidelinesegments 610A, 610B, 612A, and 612B. The unit cell 613, in effect,demonstrates the minimum repeating pattern in the fabric, and themaximum allowable pocket size. It should be noted that, while the fabricshown in FIGS. 7A through 7E has about one warp knuckle per unit cell,other fabrics may have more than one warp knuckle and/or more than oneweft knuckle per unit cell. In other words, the unit cells defined bythe knuckle patterns will vary with different fabric patterns.

As will be readily apparent to those skilled in the art, any or all ofthe steps shown in FIGS. 7A through 7E can either be performed by a useron a display screen, or alternatively, may be automated so as to beperformed upon execution of the analysis program. That is, the analysisprogram may be configured to automatically identify knuckles as thedarkened regions of images, outline the knuckles, and then draw theguidelines based on the indentified knuckles in the manner describedabove.

After the selected knuckle has been identified, and after the guidelinesestablished through the knuckles, multiple properties of the fabric maybe calculated using knuckle sizes and positions determined by theanalysis program. To perform such calculations, the knuckle size andpositioning data can be exported from the analysis program to aconventional spreadsheet program to calculate the properties of thefabric. Examples of the determinations made by the analysis program andthe calculations that follow from such determinations are shown in TABLE1.

TABLE 1 Characteristic of the Fabric Determination/Calculation KnuckleLength determined based on outline of identified warp (KL) knuckle oridentified weft knuckle Knuckle Width determined based on outline ofidentified warp (KW) knuckle or identified weft knuckle Frequency ofdetermined based on guidelines drawn through Guidelines (f) knucklesfreq 1 = frequency of one set of parallel lines (per inch or cm) freq 2= frequency of another set of parallel lines (per inch or cm) RoundingRadius (r) determined based on outline of identified warp knuckle and/oridentified weft knuckle, the rounding radius is the level of roundingthat is application to the corners of rectangular objects KnuckleDensity Per determined based on the number of warp or Unit Cell (KDUC)weft knuckles identified within a cell (knuckles per unit cell) UnitCell Knuckle warp UKA = warp KW × warp LW − ((2 × Area (UKA) warp r)² −π(warp r)²) weft UKA = weft KW × weft LW − ((2 × x weft r)² − π(weftr)²) Knuckle Density F = freq 1 × freq 2 (KD) warp KD = F × warp KDUCweft KD = F × weft KDUC Total Warp or Weft warp area % = warp KD × warpUKA Knuckle Contact weft area % = weft KD × warp UKA Area (%) ContactArea Ratio TKCA = warp area % + weft area % (Total % In-Plane KnuckleContact Area) % Area % warp AC = [warp UKA/(warp UKA + weft Contribution(AC) UKA)] × 100 % weft AC = [weft UKA/(warp UKA + weft UKA)] × 100Pocket Area PA = (1/(freq 1 × freq 2)) − (warp UKA × Estimate (PA) warpKDUC) − (weft UKA × weft KDUC) Pocket Density (PD) PD = freq 1 × freq 2(pockets per square inch or centimeter)

The fabric from which image 600 was obtained only included knuckles 602on the warp threads. Other fabrics, however, may include knuckles on theweft threads, such as the fabrics that formed the prints in FIGS. 6B and6D. With such fabrics, the knuckles on the weft threads can beidentified using the outlining technique described above, and theguidelines can be drawn through the weft knuckles using the techniquedescribed above.

While the contact surface of a fabric may be characterized by using aprint of the knuckles of the fabric that is formed, for example, by thecontact surface printing apparatus 300, in other embodiments, an imageof the contact surface of the fabric may be obtained in a differentmanner. An alternative to forming a print of the knuckles of the fabricis to photograph the knuckles of a fabric, and then use theabove-described procedures and techniques for analyzing an image formedfrom the photograph. In this regard, a photograph with 2400 dpi has beenfound to provide sufficiently high and low resolution so as to beanalyzed by the techniques described herein.

An example of a photograph 700 of the portion of a papermaking fabricwith knuckles is shown in FIG. 8A, and the application of the analyticabove-described technique to the image generated from photograph 700 areshown in FIGS. 8B and 8C. The photograph 700 in FIG. 8A shows the fabric701 next to a ruler R. When the photograph 700 is converted to an imagefor use with the analysis program, the scale for the image 700A can beinput based on the photographed ruler R. That is, ruler R in thephotograph 700 provides an input from which the analysis can apply ascale to the image. The displayed image 700A, along with the scale SC,is shown in FIG. 8B.

To identify the sizes and locations of knuckles in an image obtainedfrom a photograph of the fabric, the same techniques described aboveusing an image from a print of the fabric, may be used with thephotograph. For example, an outlined knuckle 702A and guidelines 710 and712 are shown on the image 700A in FIG. 8C. With the knuckle sizing andlocation data from the analysis program, all of the above-describedcalculations may be carried out to characterize the contact surface ofthe fabric that was photographed.

The above-described techniques provide a good estimate of the propertiesof a fabric, particularly when the shapes of the unit cells formed bythe guideline segments are substantially rectangular. In cases, however,when the shapes of the unit cells formed by the guidelines arenon-rectangular, parallelograms, an alternative technique may be used toprovide more accurate estimates of the properties of the fabrics. Anexample of this alternative technique is shown in FIG. 8A, which is animage generated from a photograph of the surface of a fabric using theabove described image analysis program. In this figure, a unit cell 813is defined by the guideline segments 810A, 810B, 812A, and 812B. Theunit cell 813 formed by the guideline segments 810A, 810B, 812A, and812B is a substantially non-rectangular, parallelogram shape. In thisparallelogram, an angle θ is defined at the corner A where guidelinesegments 810A and 812B intersect, and the angle θ is also defined at thecorner B where the guideline segments 810B and 812A intersect. Thisangle θ can be readily determined using the image analysis program basedon the difference in orientation angles of the guidelines. Further, theimage analysis program can also determine the distance between theguideline segments 810A and 810B (“DIST 1”) and the distance betweenguideline segments 812A and 812B (“DIST 2”) based on the scale of theimage in the manner generally described above. Having determined theintersecting angle θ, the DIST 1, and the DIST 2, the area of the unitcell (UCA) can be calculated using either of the Formula (1) or Formula(2):UCA=(DIST1/sin 0)×DIST2  (1)UCA=(DIST2/sin 0)×DIST1  (2)Formulas (1) and (2) are derived from the standard formula forcalculating the area of a parallelogram, namely Area=base length×height,where DIST 1 or DIST 2 is used as the height of the parallelogram, andthen base length is calculated from the sine of the angle θ and theother of DIST 1 or DIST 2.

Table 2 shows examples of determinations made by the analysis programand the calculations that follow from such determinations when using thealternative technique based on a non-rectangular, parallelogram unitcell area calculation.

TABLE 2 Characteristic of the Fabric Determination/Calculation KnuckleLength (KL) determined based on outline of identified warp knuckle oridentified weft knuckle Knuckle Width (KW) determined based on outlineof identified warp knuckle or identified weft knuckle Frequency ofdetermined based on guidelines drawn through Guidelines (f) knucklesfreq 1 = frequency of the first set of parallel lines (per inch or cm)freq 2 = frequency of the second set of parallel lines (per inch or cm)Intersecting Angle of determined based on guidelines drawn through theGuidelines (θ) knuckles θ1 = orientation angle of the first set ofparallel lines (degree) θ2 = orientation angle of the second set ofparallel lines (degree) θ = Abs (θ1 − θ2): intersecting angle betweenthe two sets of guidelines Rounding Radius (r) determined based onoutline of identified warp knuckle and/or identified weft knuckle, therounding radius is the level of rounding that is application to thecorners of rectangular objects Knuckle Density Per determined based onthe number of warp or Unit Cell (KDUC) weft knuckles identified within acell (knuckles per unit cell) Unit Cell Knuckle warp UKA = warp KW ×warp KL − ((2 × Area (UKA) warp r)² − π(warp r)²) weft UKA = weft KW ×weft KW − ((2 × weft r)² − π(weft r)²) Knuckle Density (KD) warp KD = PD× warp KDUC weft KD = PD × weft KDUC Total Warp or Weft warp area % =warp KD × warp UKA Knuckle Contact weft area % = weft KD × weft UKA Area(%) Total % In-Plane TKCA = warp area % + weft area % Knuckle ContactArea % Area Contribution % warp AC = [warp UKA/(warp UKA + weft (AC)UKA)] × 100 % weft AC = [weft UKA/(warp UKA + weft UKA)] × 100 PocketArea Estimate PA = (1/PD) − (warp UKA × warp KDUC) − (PA) (weft UKA ×weft KDUC) Pocket Density (PD) PD = freq 1 × [freq 2 × sin θ] (pocketsper square inch or centimeter)

It should be noted that, while some of the characteristics in TABLE 2are determined or calculated in the same manner as those described abovein TABLE 1, the knuckle density, the total warp or weft knuckle contactarea, the contact area ratio, the percent area contribution, the pocketarea estimate, and the pocket density characteristics are calculateddifferently in TABLE 2 than in TABLE 1. By accounting for thenon-rectangular, parallelogram shape of the unit cells, these differentcalculations provide for more accurate estimations of thecharacteristics of fabrics that have non-rectangular, parallelogramshaped unit cells.

A technique for calculating the effective volume of the pockets of astructuring fabric will now be described. The effective volume of apocket is the product of the cross-sectional area of the pocket at thesurface of the structuring fabric (i.e., between the knuckle surfaces)and the depth of the pocket into which cellulosic fibers in the web canmigrate during the papermaking process. The cross-sectional area of thepockets is the same as the estimate of the Pocket Area, as described inTABLES 1 and 2 above. The depth of pockets of a structuring fabric canbe determined, as follows.

FIG. 10 shows a magnified photograph of a structuring fabric. With thephotograph, and using the image analysis program described above, fourknuckles K1 to K4 are identified. A parallelogram has been drawn in amanner that connects the knuckles K1 to K4, with the lines of theparallelogram being drawn to not pass through the pocket area that isformed between the knuckles K1 to K4. With the parallelogram drawn, aprofile direction line PL can be drawn that passes from the knuckle K1,through the center of the pocket, to knuckle K3. The profile directionline PL will be used to determine the pocket depth using a digitalmicroscope, as described below. Note that the profile direction line PLfrom knuckle K1 and knuckle K3 passes through the center of the pocket.As will be described below, the pocket depth of a structuring fabric isdetermined as the depth in the pocket to which the cellulosic fiberscould penetrate in the paper making process. In the case of the fabricshown in FIG. 10, the maximum fiber migration depth is at the center ofthe pocket. It follows that a profile direction line could alternativelybe drawn from knuckle K2 to knuckle K4 passing through the center of thepocket, and the alternative profile direction line could be used for thepocket depth determination described below. Those skilled in the artwill also recognize that different structuring fabrics will havedifferent configurations of knuckles and pockets, but a profiledirection line could easily be determined for different structuringfabrics in the same manner as the profile direction line is determinedin FIG. 10.

FIG. 11 is a screenshot of a program used to determine the profile of apocket of the structuring fabric shown in FIG. 10. The screenshot wasformed using a VHX-1000 Digital Microscope manufactured by KeyenceCorporation of Osaka, Japan. The microscope was equipped with VHX-H3Mapplication software, also provided by Keyence Corporation. Themicroscopic image of the pocket is shown in the top portion of FIG. 11.In this image, the knuckles K′1 and K′3 and the pocket between theknuckles can easily be seen. A depth determination line DL has beendrawn from point D to point C, with the depth determination line DLpassing through the knuckles K′1 and K′3 and through the center of thepocket. The depth determination line DL is drawn to closely approximatethe profile determination line PL that is shown in FIG. 10. That is,based on inspection of the depth determination line DL derived using theknuckle and pocket image shown in FIG. 10, a user can draw the depthdetermination line DL in the microscopic image shown in FIG. 11, withthe depth determination line DL passing through the areas thatcorrespond to the knuckles K′3 and K′1 and the center portion of thepocket.

With the depth determination line DL drawn, the digital microscope canthen be instructed to calculate the depth profile of the pocket alongthe depth determination line DL, as is shown in the bottom portion ofFIG. 11. The profile of the pocket is highest at the areas correspondingto the knuckles K′3 and K′1, and the profile falls to its lowest pointat the center of the pocket. The pocket depth is determined from thisprofile as starting from the height of the knuckles K′3 and K′1, whichis marked by the line A on the depth profile. As with any two knucklesof a structuring fabric measured to this degree of precision, theknuckles K′3 and K′1 do not have the exact same height. Accordingly, theheight A is determined as an average between the two heights of theknuckles K′3 and K′ 1. The pocket depth is determined as ending at apoint just above the lowest point of the depth profile, marked by theline B on the depth profile. As those skilled in the art willappreciate, the depth of the pocket from line A to line B approximatelycorresponds to the depth in the pocket to which the cellulosic fibers inthe web can migrate in a papermaking process. Note that the VHX-H3Msoftware (discussed above) forms the full depth profile from a pluralityof slices in the thickness direction of the fabric. Also, note that informing the depth profile, the VHX-H3M software employs a filteringfunction to smooth the depth profile formed from the thickness slices.

It should be noted that the measured pocket depth will slightly varyfrom pocket to pocket in a fabric. We have found, however, that anaverage of five measured pocket depths for a structuring fabric providesa good characterization of the pocket depth. Accordingly, themeasurements of pocket depth herein, and the measurements that followfrom the measurement of the pocket depth, such as planar volumetricindex, are an average over five measured pockets for the structuringfabric.

Using the foregoing techniques, the planar volumetric index forstructuring fabrics may easily be calculated as the contact area ratio(CAR) multiplied by the effective pocket volume (EPV) multiplied by onehundred, where the EPV is the product of the pocket area estimate (PA inTABLE 1 above) and the measured pocket depth. Further, an adjustedplanar volumetric index can be calculated as the contact area ratio(CAR) multiplied by the effective pocket volume (EPV) multiplied by onehundred, where the CAR and EPV are calculated using the non-rectangular,parallelogram unit cell area calculation technique described above (theEPV being the product of the pocket area estimate PA in TABLE 2 aboveand the measured pocket depth). The planar volumetric index and adjustedplanar volumetric index for structuring fabrics used to form absorbentpaper products according to the invention will be described below. Theplanar volumetric index and adjusted volumetric index for comparativestructuring fabrics will also be described below.

Durability is another important aspect related to the structuring fabricused in a papermaking process. In particular, the web contacting surfaceformed by the knuckles in a structuring fabric is worn as thestructuring fabric is used on a papermaking machine. The wear has theeffect of increasing the size of the knuckles, which, in turn, has theeffect of increasing the contact area of the structuring fabric. At thesame time, the wear also has the effect of decreasing the pocket volumeby decreasing the pocket depth. It follows that as the contact areaincreases and the pocket depth decreases, the planar volumetric indexand adjusted planar volumetric index for the structuring fabric change.The changes in planar volumetric index and adjusted planar volumetricindex will affect the properties of the resulting paper products, forexample, by changing the size of the dome structures formed in theresulting paper products.

Sanding the contact surface of a structuring fabric is an effective wayto simulate the wear on the structuring fabric that occurs during apapermaking process. Specific amounts of the contact surface can besanded off to simulate the wear on the structuring fabric afterdifferent amounts of operation on a papermaking machine. A sandingexperiment was conducted on a fabric shown in FIG. 3 in order tosimulate wear on the fabric. TABLE 3 shows the results of the sandingexperiment by indicating properties of the structuring fabric, with theproperties having been determined according to the above-describedtechniques, particularly the technique described in TABLE 1. Morespecifically, TABLE 3 shows the initial, unsanded, properties of thefabric shown in FIG. 3 referred to as Fabric Reference A. In FabricReference B, 0.109 mm of the contact surface was removed by sanding, inFabric Reference C, 0.139 mm of the contact surface was removed bysanding, and in Reference D, 0.178 mm of the contact surface was removedby sanding.

TABLE 3 Property Units Fabric Reference A Fabric Reference B FabricReference C Fabric Reference D Amount of contact surface mm None 0.1090.139 0.178 removed In plane Warp Contact Length mm 1.68 1.88 2.03 2.18Contact Width mm 0.48 0.48 0.52 0.51 Warp Area % 22.7 25.5 29.8 31.6 Inplane Weft Contact Length mm 0.03 0.03 0.03 0.03 Contact Width mm 0.030.03 0.03 0.03 Warp Area % 0.0 0.0 0.0 0.0 Contact Area Ratio % 22.725.0 29.8 31.7 % Warp-Weft Warp Area % 1.0 1.0 1.0 1.0 Ratio Weft Area %0.0 0.0 0.0 0.0 Pocket Density 1/cm² 29.9 29.8 29.8 30.0 Fabric CellFreq R 1/cm 6.4 6.4 6.4 6.4 Definition Degree Degrees 163.5 164.5 164.5165 Freq B 1/cm 4.7 4.7 4.7 4.7 Degree Degrees 228 230 229 230 PocketDepth microns 494.2 477.9 425.3 363.8

As can be seen from the data in TABLE 3, the contact area did notsignificantly increase as sanding was applied to the structuring fabric.Without being bound by theory, it is believed that the relativelyconstant contact area can result from warp yarns of a structuring fabrichaving a substantially flat shape, as is the case with the particularfabric tested for TABLE 3. The data shown in TABLE 2 also demonstratesthat the pocket depth did not significantly decrease as the contactsurface of the fabric was sanded. With the contact area and pocket depthremaining relatively constant, it follows that the planar volumetricindex also remained relatively constant as the fabric was subjected tomore sanding. The constant planar volumetric index indicates that thefabric will be likely to produce paper products with consistentproperties through the life of the fabric on a papermaking machine.Along these lines, it has been found that the 0.109 mm of surfaceremoved in the sanding trial with Fabric Reference B closely correspondsto about 950,000 cycles of operation during a TAD process on apapermaking machine having the configuration shown in FIG. 1 (asdescribed above). The relatively small changes in the contact area andthe pocket depth in the structuring fabric after such a number of cyclesof operation is remarkable.

It should be noted that even though the unsanded fabric shown in FIG. 3and characterized as Reference A in TABLE 3 has outstanding propertiessuch as planar volumetric index, it will still often be desirable tosand the web contacting surface of the fabric before using the fabric ina papermaking operation. For example, sanding may be used to make thecontact surface of the fabric more planar prior to its initial use in apapermaking operation. It should also be noted that the term “sanding,”as used herein, is a general term intended to denote the removal of asmall amount of material from the surface of the fabric. The termsanding is not meant to be limited to any particular technique forremoving the material. For example, sanding encompasses operations thatmight also be termed “polishing,” “grinding,” or the like.

The calculated planar volumetric index and adjusted planar volumetricindex for the structuring fabric in References A to D is shown in FIG.12A. The planar volumetric index and adjusted planar volumetric indexfor Comparative Fabrics are also shown in FIG. 12A, as well as in FIGS.12B through 12D. The Comparative Fabrics are structuring fabrics thatare known in the art. A print of the fabrics showing the knuckle andpocket structure is also shown in FIGS. 12A through 12D.

The data in FIGS. 12A through 12D show the substantial differencesbetween the planar volumetric index in the structure fabric ofReferences A to D and the Comparative Fabrics 1 to 10. The planarvolumetric indexes in References A to D were between about 26 and about30, whereas the planar volumetric indexes in the Comparative Fabrics 1to 10 were much lower. Similarly, the adjusted planar volumetric indexesin References A to D were between about 27 and about 31.5, whereas theadjusted planar volumetric indexes in the Comparative Fabrics 1 to 10were much lower. Those skilled in the art will appreciate manyadvantages of the combination of contact area ratio and pocket volumethat are quantified by the planar volumetric index and adjusted planarvolumetric index of the structuring fabric in References A to D. Forexample, the greater contact area provides more of a support surface forthe web during the paper making process, in effect, providing an almostbelt-like forming surface. As another example, the greater pocket depthallows the fabric to run for a longer period of time before becoming tooworn for effective use. That is, the initially deep pockets will stillhave an effective depth even after the contact surface is substantiallyworn during a papermaking process. The deep pockets also may allow forgreater caliper products to be formed. More specifically, the caliper ofthe resulting product is partially related to the dome-structures ofproduct that are formed by portions of the web moving into the pocketsduring the papermaking process. By providing bigger pockets, thestructuring fabric of References A to D provides for larger domes,which, in turn, provide for more caliper in the final paper product.Without being bound by theory, it is believed that these aspects flowingfrom the planar volumetric indexes and adjusted planar volumetricindexes of the structuring fabric of References A to D are at leastpartially the cause of the outstanding properties of the productsaccording to our invention that are described in detail below.

Notably, the planar volumetric and adjusted planar volumetric indexesfor the fabric in References A to D are within a narrow ranges describedabove. As discussed above, References A to D simulate the wear on thefabric during its operation on a papermaking machine as shown in FIG. 1,and it has been found that Fabric Reference B correlates to about950,000 cycles of operation on the papermaking machine. Thus, when usedin a papermaking process as described above, including non-compactivelydewatering and drying the cellulosic web on the structuring fabric, thefabric of References A to D will have a planar volumetric index of atleast about 26, and a adjusted planar volumetric index of at least about27, through 950,000 cycles of operation of the papermaking machine.

The fabric that is shown and characterized in FIGS. 3 and 12A and TABLE3 can be used to form paper products, such as absorbent sheets in theform of hand towels. We have found that such paper products manufacturedwith the structuring fabric have an outstanding combination ofproperties. These properties will now be described, followed by specificexamples of products made with the structuring fabric.

As generally discussed above, one significant aspect of any paperproduct is the caliper of the product. Generally speaking, the morecaliper the better. In some embodiments of the invention, two-ply paperproducts, such as absorbent sheets, have a caliper of at least about 255mils/8 sheets. In still further embodiments of the invention, thetwo-ply paper products have a caliper of at least about 260 mils/8sheets, and further, the two-ply products have a caliper of at leastabout 265 mils/8 sheets. It should be noted that the two plies of theseproducts are directly attached without an intermediately ply, asdiscussed above. Those skilled in the art will appreciate that suchcalipers for two-ply products are, in and of themselves, outstanding.

Also discussed above is the importance of the absorbency of paperproducts, particularly in products such as absorbent hand towels. Thepaper products of our invention have exceptional absorbency, asquantified by saturation (SAT) capacity. SAT capacity is measured with asimple absorbency tester. In this test, a sample product 2.0 inches(5.08 cm) in diameter is mounted between a top flat plastic cover and abottom grooved sample plate. The sample is held in place by a ⅛ inch(0.32 cm) wide circumference flange area. The sample is not compressedby the holder. Deionized water at 73° F. (22.8° C.) is introduced to thesample at the center of the bottom sample plate through a three mmdiameter conduit. This water is at a hydrostatic head of minus five mm.Flow is initiated by a pulse introduced at the start of the measurementby the instrument mechanism. Water is thus imbibed by the sample fromthis central entrance point radially outward by capillary action. Whenthe rate of water imbibation decreases below 0.005 g water per fiveseconds, the test is terminated. The amount of water removed from thereservoir and absorbed by the sample is weighed and reported as grams ofwater per gram of sample or per square meter of sample. The absorbedamount (g/m²) is used for purposes of calculating SAT converting loss.When testing a basesheet for multi-ply towel, the number of plies usedin the towel is tested. For example, two plies of basesheet are stackedand tested, then compared with two-ply finished product made from thebasesheet for purposes of determining SAT converting loss. In practice,a Gravimetric Absorbency Testing System manufactured by M/K Systems Inc.of Danvers, Mass. is used. Water absorbent capacity (SAT) is actuallydetermined by the instrument itself. SAT is defined as the point wherethe weight versus time graph has a “zero” slope, i.e., the sample hasstopped absorbing. The termination criteria for a test are expressed inmaximum change in water weight absorbed over a fixed time period. Thisis basically an estimate of zero slope on the weight versus time graph.The program uses a change of 0.005 g over a five second time interval astermination criteria, unless “Slow SAT” is specified, in which case, thecut off criteria is one mg in 25 seconds.

In embodiments of our invention, two-ply paper products have an SATcapacity of at least about 650 g/m². In further embodiments of ourinvention, the two-ply paper products have an SAT capacity of at leastabout 675 g/m². As with the calipers for the two-ply products describedabove, these SAT capacities for two-ply paper products are, in and ofthemselves, outstanding. In fact, as will be demonstrated with thespecific examples described below, the combination of caliper and SATcapacity for the two-ply paper products according to our invention isnot found in conventional paper products.

Another significant aspect of paper products according to our inventionis related to the tensile and stretch ratios of the products. Drytensile strengths (MD and CD) and stretch at break are measured with astandard Instron® test device or other suitable elongation tensiletester that may be configured in various ways, typically, using 3 inch(76.2 mm) or 1 inch (25.4 mm) wide strips of tissue or towel,conditioned in an atmosphere of 23°±1° C. (73.4°±1° F.) at 50% relativehumidity for 2 hours. The tensile test is run at a crosshead speed of 2in/min (50.8 mm/min). The tensile ratio of a paper product is the ratioof the tensile strength of the product in the MD of the product to thetensile strength of the product in the CD. Similarly, the stretch ratioof a paper product is the ratio of the MD stretch at break to the CDstretch at break of the product.

In embodiments of our invention, paper products are provided that have atensile ratio of less than about 1.1, and in still further embodiments,paper products are provided that have a tensile ratio of less than about1.0. As will be appreciated by those skilled in the art, these tensileratios are less than the tensile ratio for other products known in theart. It follows that paper products according to our invention exhibitmore CD tensile than other paper products known in the art. The resultis that paper products according to our invention have a more consistenttensile strength in all directions, i.e., the tensile strength is aboutthe same in the MD and CD directions of the products.

In addition to the caliper, absorbency, and tensile properties, thereare other properties that are important to paper products. For example,as discussed above, the perceived softness of paper products such asabsorbent hand towels is highly desirable. But, at the same time,softness is usually inversely proportional to the absorbency and caliperof paper products. While the paper products according to our inventionhave higher absorbency and caliper than comparative paper products, thepaper products do not have a greatly reduced softness in comparison toother paper products. This can be seen in sensory softness testsconducted on the paper products. Sensory softness of the paper productscan be determined by using a panel of trained human subjects in a testarea conditioned to TAPPI standards (temperature of 71.2° F. to 74.8°F., relative humidity of 48% to 52%). The softness evaluation relies ona series of physical references with predetermined softness values thatare always available to each trained subject as they conducted thetesting. The trained subjects directly compare test samples to thephysical references to determine the softness level of the test samples.The trained subjects then assign a number to a particular paper product,with a higher sensory softness number indicating a higher the perceivedsoftness. As will be demonstrated in the specific examples of paperproducts according to our invention described below, the sensorysoftness of our inventive paper products is very good, even though theinventive products have a higher caliper and absorbency than other knownpaper products.

Those skilled in the art will recognize that there is a variety of otherimportant properties of paper products, such as the basis weight orbulk, stretch, tensile modulus, SAT rate, geometric mean (GM) break andtensile modulus, etc. In particular, the importance of basis weight orbulk to the economics of paper manufacturing is discussed above.Additional properties of the paper products according to our inventionare given for the specific examples described below.

In order to demonstrate the excellent properties of the paper productsaccording to our invention, trials were conducted wherein the productswere manufactured using a TAD process on a papermaking machine havingthe general configuration shown in FIG. 1 and described above. In thesetrials, a structuring fabric as shown in FIG. 3, and having theproperties characterized in FIG. 12A and TABLE 3, was used in thepapermaking machine. The specific experimental conditions for the trialsare shown in TABLE 4.

TABLE 4 Trials A Trials B Trials C Trials D Trials E Furnish 60% B16,60% B16, 60% B16, 60% B16, 60% B16, 40% B10, 40% B10, 40% B10, 40% B10,40% B10, Broke as available; Broke as available; Broke as available;Broke as available; Broke as available; Yankee layer 100% Yankee layer100% Yankee layer 100% Yankee layer 100% Yankee layer 100% B16 B16 B16B16 B16 Lab BW (lb/rm) OD ≥14.8 14.7 14.8 13.9 14.8 Lab Conditioned Wt≥15.3 15.1 15.3 14.3 15.3 (lb/rm), 3% M.C. Jet to Wire Ratio 1.08 1.081.08 1.08 1.08 Headbox Flow 163 163 163 163 163 (GPM/inch) Fabric Crepe<22% 12% 23% 12% 23% Reel Crepe    0%  1%  1%  1%  1% DAF Sludge SewerSewer Sewer Sewer Sewer Both LF Refiner, Adjust as needed Adjust asneeded Adjust as needed Adjust as needed Adjust as needed HPDT TicklerRefiner, Adjust as needed Adjust as needed Adjust as needed Adjust asneeded Adjust as needed HPDT Tickler Refiner Air Air Air Air Air LayerDirection Yankee Speed 3850 4000 FPM 4000 FPM 4000 FPM 4000 FPM (FPM)TAD Release 65 65 65 65 65 (mg/m²) Wet Strength Resin 16.0 lb and adjust13.0 lb/ton and 16.0 lb/ton and 15.0 lb/ton and 19.0 lb/ton and (Amrez100 HP by as needed adjust as needed adjust as needed adjust as neededadjust as needed Georgia Pacific) (lb/ton) CMC (lb/ton) 5.5 lb/ton and3.0 lb/ton and 5.5 lb/ton and 5.0 lb/ton and 8.5 lb/ton and adjust asneeded adjust as needed adjust as needed adjust as needed adjust asneeded Total Yankee coating 30 mg/m² and 30 mg/m² and 30 mg/m² and 30mg/sq m and 30 mg/sq m and add o adjust as needed adjust as neededadjust as needed adjust as needed adjust as needed mg/m² Debonder(lb/ton) 0 0 0 0 0 PVOH:PAE Ratio 56%/44% 56%/44% 56%/44% 56%/44%56%/44% Modifier (mg/m²) 1.1 1.1 1.1 1.1 1.1 Crepe blade bevel 20 20 2020 20 Angle (degrees) Post TAD2 18.0%   18.0%   18.0%   18.0%   18.0%  Moisture TAD1 0.2 0.2 0.2 0.2 0.2 Gap Pressure (WC) Headbox Charge 0 to−0.5 0 to −0.5 0 to −0.5 0 to −0.5 0 to −0.5 (ml/10 mil sample) ReelMoisture 3.0%  3.0%  3.0%  3.0%  3.0%  CMC/WSR Split 35/30/35 35/30/3535/30/35 35/30/35 35/30/35 (Y/M/A) Basesheet Physical Targets BasisWeight AD (lb/rm) 15.3(2) 16.3(2A) 15.1 15.3 14.3 15.3 Caliper(mils/8sheets) ~140 128 155 129 150 MD Dry Tensile (g/3 in.) 1350 1430 14301430 1430 CD Dry Tensile (g/3 in.) 1350 1430 1430 1430 1430 MD Stretch(%) 21 15 22 15 22 CD Wet Tensile (g/3 in.) 405 390 400 400 400 CDwet/dry (%) 30.0 27.0 28.0 28.0 28.0 LF 1&2 Refining (HPDT) >1.0/1.0Adjust as needed Adjust as needed Adjust as needed Adjust as needed

The basesheets produced in Trials A to E were converted into two-plyabsorbent sheets using standard conversion equipment. The conversionprocess included embossing using the pattern shown in U.S. Design Pat.No. 648,137 (the disclosure of which is incorporated by reference in itsentirety). The emboss penetration was set at 0.075 inches for sometrials, and at 0.120 inches for other trials. The specific convertingprocess parameters are shown in TABLE 5.

TABLE 5 Parameter Value Emboss Pattern U.S. Design Patent No. 648,137 at0.075 inches or 0.120 inches Emboss Roll Diameter 20 inches RubberBack-up Roll Hardness Durometer 55 Shore A Rubber Back-up Roll Diameter20 inches Rubber Roll Cover Thickness 0.625 inches   Marrying RollDiameter 14 inches Marrying Roll Hardness Durometer 93 Shore A Feed RollGap 0.030 inches   Line Speed (rewinder) 850 fpm (21 logs per minute)

The converted, two-ply absorbent sheets from some of the trials werethen tested to determine characteristics of the sheets, including SATcapacity, caliper, tensile ratio, stretch ratio, and sensory softness.The determined characteristics are shown in TABLES 6 and 7. Note thatthe indication “N/D” in TABLES 6 and 7 is an indication that theparameter was not measured for the particular trial.

TABLE 6 CD Wet Basis Caliper MD GM Tensile - CD Weight (mils/8 TensileCD Tensile Tensile MD Stretch CD Stretch Finch Wet/Dry - Trial(lbs/ream) sheets) (g/3 in.) (g/3 in.) (g/3 in.) (%) (%) (g/3 in.) Finch(%) Product 1 31.52 270.8 2448 2502 2475 24.7 10.7 619 24.7 Product 231.95 259.6 2802 3049 2922 23.2 10.2 831 27.3 Product 3 32.27 260.2 28233065 2941 23.4 10.1 829 27.0 Product 4 31.94 266.6 2623 2694 2658 23.010.6 741 27.5 Product 5 32.19 259.6 2775 3118 2941 24.0 10.2 889 28.5Product 6 31.94 263.1 2673 2945 2805 23.2 10.3 847 28.8 Product 7 31.54262.8 2547 2742 2642 23.1 10.3 817 29.8 Product 8 31.93 263.7 2406 27252560 23.7 10.1 777 28.5 Product 9 32.00 262.9 2492 2967 2719 23.5 10.0814 27.4 Product 10 27.73 229.6 2103 2176 2139 21.5 10.3 597 27.4Product 11 29.25 223.9 2794 2669 2730 15.2 8.6 723 27.1 Product 12 30.92235.3 3219 3097 3157 15.2 8.5 850 27.4 Product 13 31.33 216.2 3054 28632957 14.4 7.5 774 27.0 Product 14 31.41 221.1 2901 3006 2953 14.3 7.6789 26.3 Product 15 30.28 221.0 2764 2810 2787 14.2 7.3 781 27.8 Product16 31.22 218.6 3143 3132 3138 14.8 8.0 804 25.7 Product 17 30.95 216.32727 2627 2676 15.2 8.0 659 25.1 Product 18 31.30 217.4 3033 2837 293316.5 8.1 767 27.0 Product 19 31.15 219.9 3099 2921 3008 15.4 7.9 70824.2 Product 20 31.68 216.7 3111 3120 3115 15.9 8.1 781 25.0 Product 2131.56 222.5 2803 2619 2709 16.7 8.2 687 26.2 Product 22 31.44 215.4 30312975 3003 15.6 7.8 779 26.2 Product 23 31.54 222.5 3514 3168 3336 15.47.8 884 27.9 Product 24 31.48 219.6 3403 3519 3460 15.3 7.8 948 26.9

TABLE 7 GM GM Perf SAT SAT SAT Break Tensile Roll Roll Tensile CapacityCapacity Rate Modulus Modulus Diameter Compression Sensory MDS/ TensileTrial (g/3 in.) (g/m²) (g/g) (g/sec^(−1/2)) (g/%) (g/in/%) (inches) (%)Softness CDS Ratio Product 1 582 679 13.2 0.27 152.7 41.7 4.96 11.9 5.82.31 0.98 Product 2 752 708 13.6 0.34 189.8 59.6 4.94 11.6 5.5 2.27 0.92Product 3 784 705 13.4 0.39 189.3 60.3 4.94 12.0 5.3 2.30 0.92 Product 4698 706 13.6 0.37 169.8 50.0 4.98 10.8 5.9 2.17 0.97 Product 5 727 72913.9 0.40 188.4 61.0 5.03 12.8 5.3 2.36 0.89 Product 6 768 716 13.8 0.40180.6 55.8 5.01 11.4 5.3 2.24 0.91 Product 7 664 730 14.2 0.40 171.350.8 5.02 11.4 5.7 2.24 0.93 Product 8 698 716 13.8 0.39 165.5 52.9 5.0310.6 5.8 2.35 0.88 Product 9 680 726 13.9 0.40 177.0 52.3 5.06 11.3 5.65 2.34 0.84 Product 10 669 674 14.9 0.38 144.5 44.0 5.95 5.9  N/D2.09 0.97 Product 11 674 629 13.2 0.27 238.1 63.2 4.79 12.9 N/D 1.771.05 Product 12 834 598 11.9 0.30 277.5 63.9 5.35 12.4 5.2 834 N/DProduct 13 674 566 11.1 0.26 281.1 N/D N/D N/D 6.1 674 N/D Product 14735 569 11.1 0.24 284.0 N/D N/D N/D 5.9 735 N/D Product 15 N/D 577 11.70.27 273.8 N/D N/D N/D 5.9 N/D N/D Product 16 N/D 554 10.9 0.24 289.1N/D N/D N/D 5.8 N/D N/D Product 17 N/D 571 11.3 0.26 243.1 N/D N/D N/D6.6 N/D N/D Product 18 N/D 553 10.9 0.25 255.8 N/D N/D N/D 6.2 N/D N/DProduct 19 N/D 581 11.5 0.26 273.9 N/D N/D N/D 6.0 N/D N/D Product 20N/D 547 10.6 0.26 274.7 N/D N/D N/D 5.6 N/D N/D Product 21 N/D 549 10.70.25 231.5 N/D N/D N/D 6.0 N/D N/D Product 22 N/D 562 11.0 0.30 269.3N/D N/D N/D 5.8 N/D N/D Product 23 N/D 597 11.6 0.31 308.7 N/D N/D N/D5.6 N/D N/D Product 24 N/D 604 11.8 0.36 316.6 N/D N/D N/D 5.3 N/D N/D

The combination of high caliper and good absorbency of the paperproducts according to our invention is not found in other paper productsknown in the art. Evidence of this can be seen in FIG. 13, which showsthe SAT capacity in relation to caliper for products made according tothe techniques described above. FIG. 13 also shows comparative two-plyand comparative three-ply absorbent products made by the assignee of thepresent application, as well as by other manufacturers. The comparativetwo-ply and three-ply products include products made in papermakingprocesses with structuring fabrics, as well as two-ply products madewith structuring belts instead of structuring fabrics. As can be seenfrom this data, the trial products according to our invention all had anoutstanding combination of caliper and SAT capacity. Specifically, thetwo-ply trial products had a caliper of at least about 255 mils/8 sheetsand an SAT capacity of at least about 650 g/m². Further, some of thetrial products had an SAT capacity of more than 700 g/m², and four trialproducts had a caliper of greater than 265 mils/8 sheets. On the otherhand, none of the two-ply comparative products had the combination ofcaliper and SAT capacity of the two-ply trial products. The only productthat had the combination of SAT capacity and caliper was a three-plycomparative product. Of course, as will be appreciated by those skilledin the art, the cost associated with manufacturing a three-ply productis significantly greater than that for a two-ply product.

As discussed in detail above, the absorbency and caliper of paperproducts, are, in general, inversely related to the perceived softnessof the paper products. The data in TABLES 6 and 7, in combination withthe data shown in FIG. 13 demonstrates the outstanding combinationabsorbency, caliper, and softness for the products of our invention.While our inventive paper products demonstrate high absorbency andcaliper, the softness of the paper products, as indicated by the sensorysoftness values indicated in TABLES 6 and 7, was still relatively high.For comparison, similar commercially marketed hand towels may generallyhave a sensory softness of 5.1 to 6.8.

FIG. 14 shows further properties of the trial products according to ourinvention, as well as additional properties of comparative two-ply andthree-ply products. Specifically, FIG. 14 shows the relation of tensileratio and caliper for the trial products and the same comparisonproducts shown in FIG. 13. The trial products all had a tensile ratio ofless than about 1.00 with the SAT capacities of at least about 650 g/m².More specifically, the trial products had tensile ratios from about 0.85to about 1.0. On the other hand, most of the comparison products had atensile ratio of greater than 1.00. As discussed above, tensile ratiosin the ranges of the trial products provide for products that have moreconsistent strength in all directions. The comparison products havingtensile ratios significantly greater than 1.0 do not have a consistentstrength in all directions, but rather, show significantly more strengthin the MD than in the CD.

Further distinct properties of the products according to our inventioncan be seen in FIGS. 15 through 17. FIG. 15 demonstrates the SATcapacity as a function of tensile ratio for the trial products accordingto our invention and the comparison paper products. As discussed above,the two-ply trial products had SAT capacities of at least about 650g/m², and tensile ratios of about 0.85 to about 1.0. As is evident fromFIG. 15, this combination of SAT capacity and tensile ratio make thetrial products distinct from the two-ply and three-ply comparisonproducts. FIGS. 16 and 17 show the stretch ratio in relation to SATcapacity and caliper, respectively, for trial products according to theinvention and the comparison products. Once again, it can be seen thatthe trial products had unique combinations of properties that are notfound in any of the comparison products.

Although the foregoing specific examples of products had a generallynarrow range of parameters such as basis weight, absorbency, caliper,etc., that are conducive to specific commercial products, such as handtowels, it will be appreciated by those skilled in the art that thetechniques and methods disclosed herein can be used to produce a varietyof products. To demonstrate the broad scope of our invention, a varietyof basesheets was produced using the techniques described above,including a TAD process on a papermaking machine having theconfiguration shown in FIG. 1, and using the structuring fabriccharacterized in FIGS. 3 and 12A and TABLES 3 and 4. The properties ofthese basesheets are shown in TABLE 8.

TABLE 8 Caliper CD Wet Basis (mils/ MD MD CD Ten- Tensile - Base- Weight8 Tensile Stretch Tensile sile Finch sheet (lb/rm) sheets) (g/3 in.) (%)(g/3 in.) Ratio (g/3 in.) 1 17.4 158 1752 26.3 1835 0.96 514 2 15.7 1581284 24.6 1415 0.91 416 3 15.7 164 1617 27.0 1292 1.26 398 4 14.5 1431431 17.1 1397 1.03 418 5 13.5 138 1403 15.5 1285 1.09 406 6 12.6 1341429 13.8 1338 1.07 420 7 12.7 117 1466 11.7 1447 1.02 403 8 12.9 1141525 11.4 1447 1.06 432 9 13.1 133 1397 15.8 1456 0.96 419 10 12.3 1221470 13.3 1440 1.02 423 11 23.3 159 2654 27.9 2593 1.02 660 12 23.3 1623309 27.0 3158 1.05 898 13 25.0 160 2738 27.2 2772 0.99 661

The results in TABLE 8 demonstrate the wide range of properties,including basis weight, caliper, and CD wet tensile, that can beimparted to products according to our invention. Without being bound bytheory, it is believed that these properties are at least partially madepossible through the unique nature of the structuring fabric used toform the products. For example, as discussed above, the planarvolumetric index of the structuring fabric has a significant effect onthe properties of the products, and the planar volumetric index of thestructuring fabric is much different than the planar volumetric indexesof other structuring fabrics known in the art.

Although this invention has been described in certain specific exemplaryembodiments, many additional modifications and variations would beapparent to those skilled in the art in light of this disclosure. It is,therefore, to be understood that this invention may be practicedotherwise than as specifically described. Thus, the exemplaryembodiments of the invention should be considered in all respects to beillustrative and not restrictive, and the scope of the invention to bedetermined by any claims supportable by this application and theequivalents thereof, rather than by the foregoing description.

INDUSTRIAL APPLICABILITY

The invention can be used to produce desirable paper products such ashand towels. Thus, the invention is applicable to the paper productsindustry.

We claim:
 1. An absorbent cellulosic sheet made by a method thatcomprises: forming an aqueous cellulosic web on a structuring fabric ina papermaking machine; non-compactively dewatering the cellulosic web onthe structuring fabric; and drying the cellulosic web to form theabsorbent cellulosic sheet, wherein a portion of the structuring fabricon which the cellulosic web is formed has an adjusted planar volumetricindex of at least about 27, and wherein the absorbent cellulosic sheet(i) is two-ply, (ii) has a caliper of at least about 260 mils/8 sheets,and (iii) has a saturation (SAT) capacity of at least about 650 g/m². 2.The absorbent sheet according to claim 1, wherein the adjusted planarvolumetric index is about 27 to about 31.5.
 3. The absorbent sheetaccording to claim 1, wherein the sheet is multi-ply and has a basisweight of less than about 32 lbs/ream.
 4. The absorbent sheet accordingto claim 1, wherein the planar volumetric index includes two variables:the contact area ratio (CAR) and the effective pocket volume (EPV). 5.The absorbent sheet according to claim 4, wherein the contact area ratiois defined as the ratio of the contact area formed by knuckles in thestructuring fabric to an open area in the web contacting side of thestructuring fabric.
 6. The absorbent sheet according to claim 5, whereinthe effective pocket volume is defined as an average volume of pocketsin the structuring fabric into which cellulosic fibers of the web maymigrate during a papermaking operation.
 7. The absorbent sheet accordingto claim 6, wherein the planar volumetric index is defined as thecontact area ratio (CAR) multiplied by the effective pocket volume (EPV)multiplied by one hundred.
 8. The absorbent sheet according to claim 7,wherein the adjusted planar volumetric index is about 27 to about 31.5.9. An absorbent cellulosic sheet made by a method that comprises:forming an aqueous cellulosic web on a structuring fabric in apapermaking machine; non-compactively dewatering the cellulosic web onthe structuring fabric; and drying the cellulosic web to form theabsorbent cellulosic sheet, wherein a portion of the structuring fabricon which the cellulosic web is formed has an adjusted planar volumetricindex of at least about 27, and wherein the absorbent cellulosic sheet(i) is two-ply, (ii) has a caliper of at least about 260 mils/8 sheets,(iii) has a saturation (SAT) capacity of at least about 650 g/m², and(iv) a dry machine direction (MD) to cross machine direction (CD)tensile ratio of about 0.9 to about 1.0.
 10. The absorbent sheetaccording to claim 9, wherein the adjusted planar volumetric index isabout 27 to about 31.5.
 11. The absorbent sheet according to claim 9,wherein the sheet is multi-ply and has a basis weight of less than about32 lbs/ream.
 12. The absorbent sheet according to claim 9, wherein theplanar volumetric index includes two variables: the contact area ratio(CAR) and the effective pocket volume (EPV).
 13. The absorbent sheetaccording to claim 12, wherein the contact area ratio is defined as theratio of the contact area formed by knuckles in the structuring fabricto an open area in the web contacting side of the structuring fabric.14. The absorbent sheet according to claim 13, wherein the effectivepocket volume is defined as an average volume of pockets in thestructuring fabric into which cellulosic fibers of the web may migrateduring a papermaking operation.
 15. The absorbent sheet according toclaim 14, wherein the planar volumetric index is defined as the contactarea ratio (CAR) multiplied by the effective pocket volume (EPV)multiplied by one hundred.
 16. The absorbent sheet according to claim15, wherein the adjusted planar volumetric index is about 27 to about31.5.